Synthesis of LiNiO2 in air atmosphere: X-ray diffraction characterization and electrochemical investigation

The synthesis of LiNiO2 in air is studied by means of X-ray diffraction (XRD) characterization using a new fast method based on the splitting of the (108) and (110) peaks and the depth of the minimum between these peaks. From the evolution of these XRD parameters during the heat treatment of the starting mixture of LiOH and NiO the optimum synthesis time is determined, where the separation angle has a maximum, implying a good stoichiometry and low cation disorder; the minimum between the peak is deepest, indicating a better crystallinity. Selected samples of LiNiO2 were cycled as cathodes in laboratory-coin cells between constant charge and discharge end voltages at a constant current. It is found that the capacity decay rate is related to the phase transitions occurring during cycling. This rate is dependent on the minimum lithium content x in LixNi2 − xO2 at the end of charge. As the cycling proceeds xmin increases despite that the end charge voltage is kept constant, whereby the capacity decay rate diminishes.